Systems and methods for performing data management operations using snapshots

ABSTRACT

A system stores a snapshot and an associated data structure or index to storage media to create a secondary copy of a volume of data. In some cases, the associated index includes application specific data about a file system or other application that created the data to identify the location of the data. The associated index may include three entries, and may be used to facilitate the recovery of data via the snapshot. The snapshot may be used by ancillary applications to perform various functions, such as content indexing, data classification, deduplication, e-discovery, and other functions.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.12/979,101, entitled “SYSTEMS AND METHODS FOR PERFORMING DATA MANAGEMENTOPERATIONS USING SNAPSHOTS,” filed Dec. 27, 2010, which claims priorityto and the benefit of U.S. Patent Application No. 61/291,803, entitled“SYSTEMS AND METHODS FOR PERFORMING DATA MANAGEMENT OPERATIONS USINGSNAPSHOTS,” filed on Dec. 31, 2009, and is related to U.S. patentapplication Ser. No. 12/558,947 filed on Sep. 14, 2009 (entitled “USINGA SNAPSHOT AS A DATA SOURCE,”) and U.S. patent application Ser. No.12/978,984 filed on Dec. 27, 2010 (entitled “SYSTEMS AND METHODS FORANALYZING SNAPSHOTS,”), each of which is incorporated by reference inits entirety.

BACKGROUND

Current storage management systems employ a number of different methodsto perform storage operations on electronic data. For example, data canbe stored in primary storage as a primary copy or in secondary storageas various types of secondary copies including, as a backup copy, asnapshot copy, a hierarchical storage management copy (“HSM”), as anarchive copy, and as other types of copies.

A primary copy of data is generally a production copy or other “live”version of the data which is used by a software application and isgenerally in the native format of that application. Primary copy datamay be maintained in a local memory or other high-speed storage devicethat allows for relatively fast data access if necessary. Such primarycopy data is typically intended for short term retention (e.g., severalhours or days) before some or all of the data is stored as one or moresecondary copies, for example to prevent loss of data in the event aproblem occurred with the data stored in primary storage.

Secondary copies include point-in-time data and are typically forintended for long-term retention (e.g., weeks, months or years dependingon retention criteria, for example as specified in a storage policy asfurther described herein) before some or all of the data is moved toother storage or discarded. Secondary copies may be indexed so users canbrowse and restore the data at another point in time. After certainprimary copy data is backed up, a pointer or other location indicia suchas a stub may be placed in the primary copy to indicate the currentlocation of that data.

One form of secondary copy is a snapshot copy. From an end-userviewpoint, a snapshot may be seen as an instant image of the primarycopy data at a given point in time. A snapshot generally captures thedirectory structure of a primary copy volume at a particular moment intime, and also preserves file attributes and contents. In someembodiments, a snapshot may exist as a virtual file system, parallel tothe actual file system. Users typically gain a read-only access to therecord of files and directories of the snapshot. By electing to restoreprimary copy data from a snapshot taken at a given point in time, usersmay also return the current file system to the prior state of the filesystem that existed when the snapshot was taken.

A snapshot may be created instantly, using a minimum of file space, butmay still function as a conventional file system backup when stored ator near the file system. A snapshot may not actually create anotherphysical copy of all the data, but may simply create pointers that areable to map files and directories to specific disk blocks. The snapshotmay be a copy of a set of files and/or directories as they were at aparticular point in the past. That is, the snapshot is an image, orrepresentation, of a volume of data at a point in time. A snapshot maybe as a secondary copy of a primary volume of data, such as data in afile system, an Exchange server, a SQL database, an Oracle database, andso on. The snapshot may be an image of files, folders, directories, andother data objects within a volume, or an image of the blocks of thevolume.

Data storage systems utilize snapshots for a variety of reasons. Onetypical use of snapshots is to copy a volume of data without disablingaccess to the volume for a long period. After performing the snapshot,the data storage system can then copy the data set by leveraging thesnapshot of the data set. Thus, the data storage system performs a fullbackup of a primary volume when a primary volume is active andgenerating real-time data. Although performing a snapshot (i.e., takingan image of the data set) is a fast process, the snapshot is typicallynot an effective or reliable backup copy of a data set, because it doesnot actually contain the content of the data set. Restoring data fromsnapshots can be especially cumbersome, because a restoration processcannot restore the data set using snapshots alone. Recovery ofindividual files or folders can be especially cumbersome, becausetypical systems often recover an entire snapshot in order to restore anindividual file or folder imaged by the snapshot.

However, the speed of performing, or taking, a snapshot can often be agreat benefit to data storage systems that are required to store largeamounts of data. Thus, utilizing snapshots in ways other than thosedescribed above may provide significant utility to data storage systems,because snapshots are fast, are space efficient, and facilitateperforming off host data storage operations, among other advantages.

The need exists for a system that overcomes the above problems, as wellas one that provides additional benefits. Overall, the examples hereinof some prior or related systems and their associated limitations areintended to be illustrative and not exclusive. Other limitations ofexisting or prior systems will become apparent to those of skill in theart upon reading the following Detailed Description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating an example of a data storagesystem that may employ aspects of the invention

FIG. 2 is a block diagram illustrating in more detail certain componentsof a data storage system according to some examples.

FIG. 3 illustrates components of a data stream that may be utilized by adata storage system.

FIG. 4 is a block diagram illustrating a system for creating asnapshot-based secondary copy of data.

FIG. 5 is a table illustrating an index associated with a snapshot.

FIG. 6 is a flow diagram illustrating a routine for building an index.

FIG. 7 is a flow diagram illustrating a routine for restoring a dataobject using a snapshot-based secondary copy.

FIG. 8 is a flow diagram illustrating a routine for generating asecondary copy of a volume of data.

FIG. 9 is a block diagram illustrating in more detail certain componentsof a data storage system according to some examples.

FIG. 10 is a flow diagram of a process for analyzing a snapshot.

FIG. 11 is a block diagram illustrating certain components of a datastorage system according to some examples.

FIG. 12 is a flow diagram of a process for creating snapshots of virtualmachines.

DETAILED DESCRIPTION

The headings provided herein are for convenience only and do notnecessarily affect the scope or meaning of the claimed invention.

Overview

Described in detail herein is a system and method that employs snapshotsas data sources, such as backup copies of data. Instead of treating asnapshot only as a picture of a disk, the system employs snapshots as adata source that can be backed up or otherwise copied to tape ormagnetic disk. The system can then seamlessly restore individual filesfrom tape or disk using snapshots. The system creates a data structure,such as an index, that describes what is on a disk (as often defined bya file system for that disk). The index may provide a list of files onthe disk, and location information indicating where each file islocated, with respect to the snapshot.

In some examples, the system creates a secondary copy of data by storinga snapshot with an index associated with and/or related to the snapshot.The snapshot identifies the data stored in the secondary copy, and theindex provides application specific context information that facilitatesretrieving data identified by the snapshot. In these examples, thesystem may store a combination of a snapshot and associated index tostorage media, such as to tape or disk, and use the stored combinationas a data source, such as a backup copy of a primary volume of data.

The system may create the index in a number of ways, as long as theindex can be used in combination with a snapshot to facilitate datastorage and/or recovery via the snapshot. For example, an index agentmay receive a snapshot of a data set, receive application contextinformation associated with the snapshot, store the snapshot, and storethe application context information in an index that identifiesindividual files from the data set imaged by the snapshot.

In some examples, the system provides for the recovery, or restoration,of data from a snapshot-based data source. The recovery may betransparent to a user (that is, the user does not know what mechanism isused during a restore process) and/or seamless with respect to othertypes of data sources. For example, the system may restore a data set byrestoring a full backup of the data set using a snapshot-based secondarycopy of the data set and incremental backups using other secondarycopies.

In some cases, the system restores individual files using snapshots andassociated indices. For example, the system may receive a request torestore a specific file or portion of a file, identify a snapshotcontaining an image of a volume containing the file, look to an indexassociated with the snapshot to identify the file, and retrieve the file(or a copy of the file) from information in the associated index. Thus,the system facilitates granular recovery of data objects within a dataset without requiring a data recovery system to restore entire snapshotsor secondary copies.

The system also facilitates techniques for enabling ancillaryapplications to perform functions using the snapshot data. Ancillaryapplications, such as indexing and search applications, electronicdiscovery applications, information management applications, taggingapplications, as well as other applications, may require secondarycopies to be in a specific format. In some examples, the techniquesdescribed herein provide an interface to snapshot data that is the same(or at least substantially similar) as an interface used to accesssecondary copies of data created using other techniques, such as backupor copy techniques. Accordingly, ancillary applications can performfunctions on snapshot data using the same techniques used to performfunctions on other secondary copies of data.

Various examples of the invention will now be described. The followingdescription provides specific details for a thorough understanding andenabling description of these examples. One skilled in the relevant artwill understand, however, that the invention may be practiced withoutmany of these details. Likewise, one skilled in the relevant art willalso understand that the invention may include many other obviousfeatures not described in detail herein. Additionally, some well-knownstructures or functions may not be shown or described in detail below,so as to avoid unnecessarily obscuring the relevant description.

The terminology used below is to be interpreted in its broadestreasonable manner, even though it is being used in conjunction with adetailed description of certain specific examples of the invention.Indeed, certain terms may even be emphasized below; however, anyterminology intended to be interpreted in any restricted manner will beovertly and specifically defined as such in this Detailed Descriptionsection.

FIGS. 1 and 2 and the discussion herein provide a brief, generaldescription of suitable specialized environments in which aspects of theinvention can be implemented. Those skilled in the relevant art willappreciate that aspects of the invention can be practiced with othercommunications, data processing, or computer system configurations,including: Internet appliances, hand-held devices (including personaldigital assistants (PDAs)), wearable computers, all manner of cellularphones, mobile phones, and/or mobile devices, multi-processor systems,microprocessor-based or programmable consumer electronics, set-topboxes, network PCs, mini-computers, mainframe computers, and the like.The terms “computer,” “server,” “host,” “host system,” and the like aregenerally used interchangeably herein, and refer to any of the abovedevices and systems, as well as any data processor.

While aspects of the invention, such as certain functions, are describedas being performed exclusively on a single device, the invention canalso be practiced in distributed environments where functions or modulesare shared among disparate processing devices, which are linked througha communications network, such as a Local Area Network (LAN), Wide AreaNetwork (WAN), and/or the Internet. In a distributed computingenvironment, program modules may be located in both local and remotememory storage devices.

Aspects of the invention may be stored or distributed on tangiblecomputer-readable media, including magnetically or optically readablecomputer discs, hard-wired or preprogrammed chips (e.g., EEPROMsemiconductor chips), nanotechnology memory, biological memory, or otherdata storage media. Alternatively, computer implemented instructions,data structures, screen displays, and other data under aspects of theinvention may be distributed over the Internet or over other networks(including wireless networks), on a propagated signal on a propagationmedium (e.g., an electromagnetic wave(s), a sound wave, etc.) over aperiod of time, or they may be provided on any analog or digital network(packet switched, circuit switched, or other scheme).

Aspects of the invention will now be described in detail with respect toFIGS. 1 through 10. FIGS. 1-3, 9, and 11 illustrate various componentsof a data storage system that may employ aspects of the invention. FIG.1 illustrates an example data storage system. FIG. 2 illustrates in moredetail certain components of the example data storage system of FIG. 1.FIG. 3 illustrates components of a data stream that may be utilized by adata storage system in performing data storage operations. FIG. 9illustrates in more detail certain components of the example datastorage system of FIG. 1. FIG. 11 illustrates certain components of aclient in a data storage system according to some examples.

FIG. 4 illustrates a system for creating a snapshot-based on a secondarycopy of data. FIG. 5 illustrates an index associated with a snapshot.

FIGS. 6-8 and 10 are process flow diagrams. FIG. 6 illustrates a routinefor building an index. FIG. 7 illustrates a routine for restoring a dataobject using a snapshot-based secondary copy. FIG. 8 illustrates aroutine for generating a secondary copy of a volume of data. FIG. 10illustrates a process for analyzing snapshot data. FIG. 10 illustrates aprocess for analyzing a snapshot. FIG. 12 illustrates a process forcreating snapshots of virtual machines and either verifying suchsnapshots, analyzing the data of the virtual machines, or both.

Suitable Data Storage System

FIG. 1 illustrates an example of one arrangement of resources in acomputing network, comprising a data storage system 150. The resourcesin the data storage system 150 may employ the processes and techniquesdescribed herein. The system 150 includes a storage manager 105, one ormore data agents 195, one or more secondary storage computing devices165, one or more storage devices 115, one or more computing devices 130(called clients 130), one or more data or information stores 160 and162, and a single instancing database 123. The storage manager 105includes an index 111, a jobs agent 120, an interface agent 125, and amanagement agent 131. The system 150 may represent a modular storagesystem such as the CommVault QiNetix system, and also the CommVaultGALAXY backup system, available from CommVault Systems, Inc. ofOceanport, N.J., aspects of which are further described in thecommonly-assigned U.S. patent application Ser. No. 09/610,738, now U.S.Pat. No. 7,035,880, the entirety of which is incorporated by referenceherein. The system 150 may also represent a modular storage system suchas the CommVault Simpana system, also available from CommVault Systems,Inc.

The system 150 may generally include combinations of hardware andsoftware components associated with performing storage operations onelectronic data. Storage operations include copying, backing up,creating, storing, retrieving, and/or migrating primary storage data(e.g., data stores 160 and/or 162) and secondary storage data (which mayinclude, for example, snapshot copies, backup copies, hierarchicalstorage management (HSM) copies, archive copies, and other types ofcopies of electronic data stored on storage devices 115). The system 150may provide one or more integrated management consoles for users orsystem processes to interface with in order to perform certain storageoperations on electronic data as further described herein. Suchintegrated management consoles may be displayed at a central controlfacility or several similar consoles distributed throughout multiplenetwork locations to provide global or geographically specific networkdata storage information.

In one example, storage operations may be performed according to variousstorage preferences, for example, as expressed by a user preference, astorage policy, a schedule policy, and/or a retention policy. A “storagepolicy” is generally a data structure or other information source thatincludes a set of preferences and other storage criteria associated withperforming a storage operation. The preferences and storage criteria mayinclude, but are not limited to, a storage location, relationshipsbetween system components, network pathways to utilize in a storageoperation, data characteristics, compression or encryption requirements,preferred system components to utilize in a storage operation, a singleinstancing or variable instancing policy to apply to the data, and/orother criteria relating to a storage operation. For example, a storagepolicy may indicate that certain data is to be stored in the storagedevice 115, retained for a specified period of time before being aged toanother tier of secondary storage, copied to the storage device 115using a specified number of data streams, etc.

A “schedule policy” may specify a frequency with which to performstorage operations and a window of time within which to perform them.For example, a schedule policy may specify that a storage operation isto be performed every Saturday morning from 2:00 a.m. to 4:00 a.m. A“retention policy” may specify how long data is to be retained atspecific tiers of storage or what criteria must be met before data maybe pruned or moved from one tier of storage to another tier of storage.In some cases, the storage policy includes information generallyspecified by the schedule policy and/or the retention policy. (Putanother way, the storage policy includes the schedule policy and/or theretention policy.) Storage policies, schedule policies and/or retentionpolicies may be stored in a database of the storage manager 105, toarchive media as metadata for use in restore operations or other storageoperations, or to other locations or components of the system 150.

The system 150 may comprise a storage operation cell that is one ofmultiple storage operation cells arranged in a hierarchy or otherorganization. Storage operation cells may be related to backup cells andprovide some or all of the functionality of backup cells as described inthe assignee's U.S. patent application Ser. No. 09/354,058, now U.S.Pat. No. 7,395,282, which is incorporated herein by reference in itsentirety. However, storage operation cells may also perform additionaltypes of storage operations and other types of storage managementfunctions that are not generally offered by backup cells.

Storage operation cells may contain not only physical devices, but alsomay represent logical concepts, organizations, and hierarchies. Forexample, a first storage operation cell may be configured to perform afirst type of storage operations such as HSM operations, which mayinclude backup or other types of data migration, and may include avariety of physical components including a storage manager 105 (ormanagement agent 131), a secondary storage computing device 165, aclient 130, and other components as described herein. A second storageoperation cell may contain the same or similar physical components;however, it may be configured to perform a second type of storageoperations, such as storage resource management (SRM) operations, andmay include monitoring a primary data copy or performing other known SRMoperations.

Thus, as can be seen from the above, although the first and secondstorage operation cells are logically distinct entities configured toperform different management functions (i.e., HSM and SRM,respectively), each storage operation cell may contain the same orsimilar physical devices. Alternatively, different storage operationcells may contain some of the same physical devices and not others. Forexample, a storage operation cell configured to perform SRM tasks maycontain a secondary storage computing device 165, client 130, or othernetwork device connected to a primary storage volume, while a storageoperation cell configured to perform HSM tasks may instead include asecondary storage computing device 165, client 130, or other networkdevice connected to a secondary storage volume and not contain theelements or components associated with and including the primary storagevolume. (The term “connected” as used herein does not necessarilyrequire a physical connection; rather, it could refer to two devicesthat are operably coupled to each other, communicably coupled to eachother, in communication with each other, or more generally, refer to thecapability of two devices to communicate with each other.) These twostorage operation cells, however, may each include a different storagemanager 105 that coordinates storage operations via the same secondarystorage computing devices 165 and storage devices 115. This“overlapping” configuration allows storage resources to be accessed bymore than one storage manager 105, such that multiple paths exist toeach storage device 115 facilitating failover, load balancing, andpromoting robust data access via alternative routes.

Alternatively or additionally, the same storage manager 105 may controltwo or more storage operation cells (whether or not each storageoperation cell has its own dedicated storage manager 105). Moreover, incertain embodiments, the extent or type of overlap may be user-defined(through a control console) or may be automatically configured tooptimize data storage and/or retrieval.

The clients 130 typically include application software for performingvarious operations. Clients 130 typically also include an operatingsystem on which the application software runs. A file system can beprovided to facilitate and control file access by the operating systemand application software. File systems can facilitate access to localand remote storage devices for file or data access and storage. Clients130 can also include local storage such as a media module media drivewith fixed or removable media.

In some examples, the clients 130 include storage mechanisms forallowing computer programs or other instructions or data to be loadedinto memory for execution. Such storage mechanisms might include, forexample, a fixed or removable storage unit and an interface. Examples ofsuch storage units and interfaces can include a program cartridge andcartridge interface, a removable memory (for example, a flash memory orother removable memory module) and memory slot, a PCMCIA slot and card,and other fixed or removable storage units and interfaces that allowsoftware and data to be transferred from the storage unit to memory.

Data agent 195 may be a software module or part of a software modulethat is generally responsible for performing storage operations on thedata of the client 130 stored in data store 160/162 or other memorylocation. Each client 130 may have at least one data agent 195 and thesystem 150 can support multiple clients 130. Data agent 195 may bedistributed between client 130 and storage manager 105 (and any otherintermediate components), or it may be deployed from a remote locationor its functions approximated by a remote process that performs some orall of the functions of data agent 195.

As used herein, the term module might describe a given unit offunctionality that can be performed in accordance with one or moreembodiments of the present invention. As used herein, a module might beimplemented utilizing any form of hardware, software, firmware, or acombination thereof. For example, one or more processors, controllers,ASICs, PLAs, logical components, software routines or other mechanismsmight be implemented to make up a module. In implementation, the variousmodules described herein might be implemented as discrete modules or thefunctions and features described can be shared in part or in total amongone or more modules. In other words, as would be apparent to one ofordinary skill in the art after reading this description, the variousfeatures and functionality described herein may be implemented in anygiven application and can be implemented in one or more separate orshared modules in various combinations and permutations. Even thoughvarious features or elements of functionality may be individuallydescribed or claimed as separate modules, one of ordinary skill in theart will understand that these features and functionality can be sharedamong one or more common software and hardware elements, and suchdescription shall not require or imply that separate hardware orsoftware components are used to implement such features orfunctionality.

The overall system 150 may employ multiple data agents 195, each ofwhich may perform storage operations on data associated with a differentapplication. For example, different individual data agents 195 may bedesigned to handle Microsoft Exchange data, Lotus Notes data, MicrosoftWindows file system data, Microsoft Active Directory Objects data,Microsoft SQL Server data, Microsoft Sharepoint Server data, and othertypes of data known in the art. Other embodiments may employ one or moregeneric data agents 195 that can handle and process multiple data typesrather than using the specialized data agents described above.

If a client 130 has two or more types of data, one data agent 195 may berequired for each data type to perform storage operations on the data ofthe client 130. For example, to back up, migrate, and restore all thedata on a Microsoft Exchange server, the client 130 may use oneMicrosoft Exchange Mailbox data agent 195 to back up the Exchangemailboxes, one Microsoft Exchange Database data agent 195 to back up theExchange databases, one Microsoft Exchange Public Folder data agent 195to back up the Exchange Public Folders, and one Microsoft Windows FileSystem data agent 195 to back up the file system of the client 130.These data agents 195 would be treated as four separate data agents 195by the system even though they reside on the same client 130.

Alternatively, the overall system 150 may use one or more generic dataagents 195, each of which may be capable of handling two or more datatypes. For example, one generic data agent 195 may be used to back up,migrate and restore Microsoft Exchange Mailbox data and MicrosoftExchange Database data while another generic data agent 195 may handleMicrosoft Exchange Public Folder data and Microsoft Windows File Systemdata, etc.

Data agents 195 may be responsible for arranging or packing data to becopied or migrated into a certain format such as an archive file.Nonetheless, it will be understood that this represents only oneexample, and any suitable packing or containerization technique ortransfer methodology may be used if desired. Such an archive file mayinclude metadata, a list of files or data objects copied, the file, anddata objects themselves. Moreover, any data moved by the data agents maybe tracked within the system by updating indexes associated withappropriate storage managers 105 or secondary storage computing devices165. As used herein, a file or a data object refers to any collection orgrouping of bytes of data that can be viewed as one or more logicalunits.

Generally speaking, storage manager 105 may be a software module orother application that coordinates and controls storage operationsperformed by the system 150. Storage manager 105 may communicate withsome or all elements of the system 150, including clients 130, dataagents 195, secondary storage computing devices 165, and storage devices115, to initiate and manage storage operations (e.g., backups,migrations, data recovery operations, etc.).

Storage manager 105 may include a jobs agent 120 that monitors thestatus of some or all storage operations previously performed, currentlybeing performed, or scheduled to be performed by the system 150. (One ormore storage operations are alternatively referred to herein as a “job”or “jobs.”) Jobs agent 120 may be communicatively coupled to aninterface agent 125 (e.g., a software module or application). Interfaceagent 125 may include information processing and display software, suchas a graphical user interface (“GUI”), an application programminginterface (“API”), or other interactive interface through which usersand system processes can retrieve information about the status ofstorage operations. For example, in an arrangement of multiple storageoperations cell, through interface agent 125, users may optionally issueinstructions to various storage operation cells regarding performance ofthe storage operations as described and contemplated herein. Forexample, a user may modify a schedule concerning the number of pendingsnapshot copies or other types of copies scheduled as needed to suitparticular needs or requirements. As another example, a user may employthe GUI to view the status of pending storage operations in some or allof the storage operation cells in a given network or to monitor thestatus of certain components in a particular storage operation cell(e.g., the amount of storage capacity left in a particular storagedevice 115).

Storage manager 105 may also include a management agent 131 that istypically implemented as a software module or application program. Ingeneral, management agent 131 provides an interface that allows variousmanagement agents 131 in other storage operation cells to communicatewith one another. For example, assume a certain network configurationincludes multiple storage operation cells hierarchically arranged orotherwise logically related in a WAN or LAN configuration. With thisarrangement, each storage operation cell may be connected to the otherthrough each respective interface agent 125. This allows each storageoperation cell to send and receive certain pertinent information fromother storage operation cells, including status information, routinginformation, information regarding capacity and utilization, etc. Thesecommunications paths may also be used to convey information andinstructions regarding storage operations.

For example, a management agent 131 in a first storage operation cellmay communicate with a management agent 131 in a second storageoperation cell regarding the status of storage operations in the secondstorage operation cell. Another illustrative example includes the casewhere a management agent 131 in a first storage operation cellcommunicates with a management agent 131 in a second storage operationcell to control storage manager 105 (and other components) of the secondstorage operation cell via management agent 131 contained in storagemanager 105.

Another illustrative example is the case where management agent 131 in afirst storage operation cell communicates directly with and controls thecomponents in a second storage operation cell and bypasses the storagemanager 105 in the second storage operation cell. If desired, storageoperation cells can also be organized hierarchically such thathierarchically superior cells control or pass information tohierarchically subordinate cells or vice versa.

Storage manager 105 may also maintain an index, a database, or otherdata structure 111. The data stored in database 111 may be used toindicate logical associations between components of the system, userpreferences, management tasks, media containerization and data storageinformation or other useful data. For example, the storage manager 105may use data from database 111 to track logical associations betweensecondary storage computing device 165 and storage devices 115 (ormovement of data as containerized from primary to secondary storage).

Generally speaking, the secondary storage computing device 165, whichmay also be referred to as a media agent, may be implemented as asoftware module that conveys data, as directed by storage manager 105,between a client 130 and one or more storage devices 115 such as a tapelibrary, a magnetic media storage device, an optical media storagedevice, or any other suitable storage device. In one embodiment,secondary storage computing device 165 may be communicatively coupled toand control a storage device 115. A secondary storage computing device165 may be considered to be associated with a particular storage device115 if that secondary storage computing device 165 is capable of routingand storing data to that particular storage device 115.

In operation, a secondary storage computing device 165 associated with aparticular storage device 115 may instruct the storage device to use arobotic arm or other retrieval means to load or eject a certain storagemedia, and to subsequently archive, migrate, or restore data to or fromthat media. Secondary storage computing device 165 may communicate witha storage device 115 via a suitable communications path such as a SCSIor Fibre Channel communications link. In some embodiments, the storagedevice 115 may be communicatively coupled to the storage manager 105 viaa SAN.

Each secondary storage computing device 165 may maintain an index, adatabase, or other data structure 161 that may store index datagenerated during storage operations for secondary storage (SS) asdescribed herein, including creating a metabase (MB). For example,performing storage operations on Microsoft Exchange data may generateindex data. Such index data provides a secondary storage computingdevice 165 or other external device with a fast and efficient mechanismfor locating data stored or backed up. Thus, a secondary storagecomputing device index 161, or a database 111 of a storage manager 105,may store data associating a client 130 with a particular secondarystorage computing device 165 or storage device 115, for example, asspecified in a storage policy, while a database or other data structurein secondary storage computing device 165 may indicate wherespecifically the data of the client 130 is stored in storage device 115,what specific files were stored, and other information associated withstorage of the data of the client 130. In some embodiments, such indexdata may be stored along with the data backed up in a storage device115, with an additional copy of the index data written to index cache ina secondary storage device. Thus the data is readily available for usein storage operations and other activities without having to be firstretrieved from the storage device 115.

Generally speaking, information stored in cache is typically recentinformation that reflects certain particulars about operations that haverecently occurred. After a certain period of time, this information issent to secondary storage and tracked. This information may need to beretrieved and uploaded back into a cache or other memory in a secondarycomputing device before data can be retrieved from storage device 115.In some embodiments, the cached information may include informationregarding format or containerization of archives or other files storedon storage device 115.

One or more of the secondary storage computing devices 165 may alsomaintain one or more single instance databases 123. Single instancing(alternatively called data deduplication) generally refers to storing insecondary storage only a single instance of each data object (or datablock) in a set of data (e.g., primary data). More details as to singleinstancing may be found in one or more of the followingcommonly-assigned U.S. patent applications: 1) U.S. patent applicationSer. No. 11/269,512 (entitled SYSTEM AND METHOD TO SUPPORT SINGLEINSTANCE STORAGE OPERATIONS); 2) U.S. patent application Ser. No.12/145,347 (entitled APPLICATION-AWARE AND REMOTE SINGLE INSTANCE DATAMANAGEMENT); or 3) U.S. patent application Ser. No. 12/145,342 (entitledAPPLICATION-AWARE AND REMOTE SINGLE INSTANCE DATA MANAGEMENT, 4) U.S.patent application Ser. No. 11/963,623 (entitled SYSTEM AND METHOD FORSTORING REDUNDANT INFORMATION); 5) U.S. patent application Ser. No.11/950,376 (entitled SYSTEMS AND METHODS FOR CREATING COPIES OF DATASUCH AS ARCHIVE COPIES); 6) U.S. patent application Ser. No. 12/565,576(entitled SYSTEMS AND METHODS FOR MANAGING SINGLE INSTANCING DATA; or 7)U.S. patent application Ser. No. 12/647,906 (entitled BLOCK-LEVEL SINGLEINSTANCING), each of which is incorporated by reference herein in itsentirety.

In some examples, the secondary storage computing devices 165 maintainone or more variable instance databases. Variable instancing generallyrefers to storing in secondary storage one or more instances, but fewerthan the total number of instances, of each data block (or data object)in a set of data (e.g., primary data). More details as to variableinstancing may be found in the commonly-assigned U.S. patent applicationSer. No. 12/649,454 (entitled STORING A VARIABLE NUMBER OF INSTANCES OFDATA OBJECTS).

In some embodiments, certain components may reside and execute on thesame computer. For example, in some embodiments, a client 130 such as adata agent 195, or a storage manager 105, coordinates and directs localarchiving, migration, and retrieval application functions as furtherdescribed in the previously-referenced U.S. patent application Ser. No.09/610,738. This client 130 can function independently or together withother similar clients 130.

As shown in FIG. 1, each secondary storage computing device 165 has itsown associated metabase 161. Each client 130 may also have its ownassociated metabase 170. However in some embodiments, each “tier” ofstorage, such as primary storage, secondary storage, tertiary storage,etc., may have multiple metabases or a centralized metabase, asdescribed herein. For example, rather than a separate metabase or indexassociated with each client 130 in FIG. 1, the metabases on this storagetier may be centralized. Similarly, second and other tiers of storagemay have either centralized or distributed metabases. Moreover, mixedarchitecture systems may be used if desired, that may include a firsttier centralized metabase system coupled to a second tier storage systemhaving distributed metabases and vice versa, etc.

Moreover, in operation, a storage manager 105 or other management modulemay keep track of certain information that allows the storage manager105 to select, designate, or otherwise identify metabases to be searchedin response to certain queries as further described herein. Movement ofdata between primary and secondary storage may also involve movement ofassociated metadata and other tracking information as further describedherein.

In some examples, primary data may be organized into one or moresub-clients. A sub-client is a portion of the data of one or moreclients 130, and can contain either all of the data of the clients 130or a designated subset thereof. As depicted in FIG. 1, the data store162 includes two sub-clients. For example, an administrator (or otheruser with the appropriate permissions; the term administrator is usedherein for brevity) may find it preferable to separate email data fromfinancial data using two different sub-clients having different storagepreferences, retention criteria, etc.

Referring to FIG. 2, a block diagram illustrating an example ofcomponents of a server used in data storage operations is shown. Aserver, such as storage manager 105, may communicate with clients 130 todetermine data to be copied to storage media. As described above, thestorage manager 105 may contain a jobs agent 120, a management agent131, a database 111, a stream agent 210, an interface agent 125, and/orother agents 220. Jobs agent 120 may manage and control the schedulingof jobs (such as copying data files) from clients 130 to storage devices115. Management agent 131 may control the overall functionality andprocesses of the data storage system, or may communicate with globalmanagers. Database 111 or another data structure may store storagepolicies, schedule policies, retention policies, or other information,such as historical storage statistics, storage trend statistics, and soon. Interface agent 124 may interact with a user interface, enabling thesystem to present information to administrators and receive feedback orother input from the administrators or with other components of thesystem (such as via APIs). The other agents 220 may perform additionalfunctions.

Referring to FIG. 3, a block diagram illustrating components of a datastream 310 that may be utilized by a data storage system is shown. Thestream 310 may originate from a client 130, continue (as indicated byreference character 320) to a media agent 165 and then (as indicated byreference character 330) to a secondary storage device 115. For example,in storage operations, the system may store, receive and/or prepare datato be stored, copied or backed up at a server or client 130. The systemmay then transfer the data to be stored to media agent 165, which maythen refer to storage policies, schedule policies, and/retentionpolicies (and other policies) to choose a secondary storage device 115.The media agent 165 may include a snapshot agent and an index agent(although these agents may also be separate components). The secondarystorage device 115 receives the data from the media agent 165 and storesthe data as a secondary copy. Secondary storage devices may be magnetictapes, optical disks, USB and other similar media, disk and tape drives,and so on. Of course, the data storage system may employ otherconfigurations of stream components not shown in FIG. 3.

Snapshots as Data Sources, Such as Backup Copies of a Data Set

The system may store one or more snapshots with an associated index inorder to create a snapshot-based data source, such as a secondary copyof a primary volume of data. Data may be stored in various types ofvolumes, including primary copies or production copies, as well asvarious secondary copies, such as snapshots, backup copies, archivalcopies, and so on.

The system creates snapshots of blocks or chunks of data in a data storeand an associated index that keeps track of the files imaged by thesnapshot (e.g., which blocks are associated with which files and whatapplications are associated with the files). Thus, a snapshot becomes away of storing data that includes application specific data. Thesnapshots and associated index can then be used as auxiliary copies,synthetic full copies, partial or full restores, and other secondarycopies. Using snapshots as a data source allow a data storage system tobe very flexible. Also, the system can manage the snapshots, such as bybacking them up and deleting any original versions from the system.

The system creates snapshots using a variety of mechanisms. In someexamples, the system employs hardware-based snapshot mechanisms whencreating snapshots. Examples of suitable hardware-based snapshotmechanisms include EMC's Symmetrix and Clarion, Hitachi Data Storage(HDS), Network Appliance's Snapshot, and so on.

In some examples, the system employs software-based snapshot mechanisms.For example, the system may leverage continuous data replication (CDR)or discrete data replication (DDR) when creating snapshots of a volumeof data. CDR generates recovery points for a volume, which can be usedas a point in time snapshot of a volume. Thus, leveraging the recoverypoints as snapshots enables the system to generate point-in-time copies(snapshots) of a volume of data while maintaining a live copy of thevolume. Of course, other mechanisms are possible.

Further, if the data storage system employs hardware having particularcapabilities, such as the ability to take mirror copies or multiplesnapshots, that functionality may be utilized by the snapshot andassociated index. Further, snapshots may be manipulated with applicationprogramming interfaces (APIs) provided by hardware and softwareproviders.

Referring to FIG. 4, a block diagram illustrating a system for creatinga snapshot-based secondary copy of data is shown. A media agent 112includes a snapshot agent 410 and an index agent 420. The snapshot agent410 creates a snapshot 415 of a primary data store or volume, and theindex agent 420 creates an index 425 associated with the snapshot 415.The media agent 112 stores the snapshot 415 and index 425 as a secondarycopy 430, which may be a backup copy, archive copy, and so on. Thesecondary copy 430, or snapshot-based secondary copy, is stored onstorage media 113, such as magnetic tape, optical disk, magnetic disk,and so on. In some cases, the snapshot and index are logically linkedwithin the secondary copy or across resources in a data storageenterprise. The storage media 113 may be located remotely from the mediaagent, or may be relocated to a geographically remote location aftercreation and storage of the secondary copy 430 is complete.

The system may employ a number of different mechanisms when movingsnapshots to secondary storage, such as magnetic tape. In some examples,the system performs block-level or chunk-based migration or transfer ofsnapshots from primary storage to secondary storage.

Briefly, block-level migration, or block-based data migration, involvestransferring or migrating disk blocks from a primary data store (e.g., adisk partition or volume) to secondary media. Using block-levelmigration, a data storage system transfers blocks on a disk that havenot been recently accessed to secondary storage, freeing up space on thedisk. Chunked file migration, or chunk-based data migration, involvessplitting a data object into two or more portions of the data object,creating an index that tracks the portions, and storing the data objectto secondary storage via the two or more portions. Among other things,the chunk-based migration provides for fast and efficient storage of adata object. Additionally, chunk-based migration facilitates fast andefficient recall of a data object, such as a snapshot of a largedatabase or virtual machine file. For example, if a user modifies amigrated file, chunk-based migration enables a data restore component toonly retrieve from, and migrate back to, secondary storage the chunkcontaining the modified portion of the file, and not the entire file.Further details regarding block-level and/or chunk-based data migrationmay be found in U.S. patent application Ser. No. 12/553,199 entitledTRANSFERRING OR MIGRATING PORTIONS OF DATA OBJECTS, SUCH AS BLOCK-LEVELDATA MIGRATION OR CHUNK-BASED DATA MIGRATION, which is herebyincorporated by reference in its entirety.

The snapshot agent 410 creates, takes, produces, and/or generates asnapshot or multiple snapshots of a data source, such as a primaryvolume of data or a secondary copy of a primary volume. As discussedherein, the snapshot is a representation of a set of data objects at agiven point in time. The snapshot may be a complete image of a data set,or may be an incremental image of a data set. Further details withrespect to the snapshot process and the types of snapshots may be foundin U.S. patent application Ser. No. 10/990,353, filed on Nov. 15, 2004,entitled SYSTEM AND METHOD FOR PERFORMING AN IMAGE LEVEL SNAPSHOT ANDFOR RESTORING PARTIAL VOLUME DATA.

Information regarding a snapshot is stored in a data structure. Forexample, a data structure may be generally organized like the followingdata structure:

{ Snapshot Identifiers Snapshot Engine Identifiers Source IdentifiersDestination Identifiers Creation Time Snapshot Group IdentifiersSnapshot Type Storage Operation Identifiers Flags Snapshot PruningInformation }

In the above data structure, the Snapshot Identifiers may includeinformation used to uniquely identify the snapshot. The Snapshot EngineIdentifiers may include information used to identify the engine thatperformed the snapshot. Source Identifiers and Destination Identifiersmay include information about the source of the data of which a snapshotwas made and where the snapshot is stored, respectively. Creation Timemay be a timestamp indicating when the snapshot was made. The SnapshotGroup Identifiers may identify a group to which the snapshot belongs.The Snapshot Type may include information identifying a type of thesnapshot. The Storage Operation Identifiers may include informationidentifying a storage operation and/or storage operation elementsassociated with the snapshot. Flags may include one or more flags orbits set to indicate various types of information regarding thesnapshot, and Snapshot Pruning Information may include information aboutwhether or not the snapshot can be pruned.

The index agent 420 creates, generates, and/or builds a data structure,such as an index, to be associated with one or more snapshots. Asdescribed more fully below, the index may be a two tier index, may be athree tier index, or may have other index configurations, depending onthe needs of the system. The two tier index may include a first entrythat contains information identifying a data object, such as a file orfolder, and a second entry that identifies where the file or folder islocated. As an alternative, the second entry may indicate where anarchive file (the file stripped of its native format) is located.

The three tier index includes the first and second entries as well as athird entry that contains the application specific data discussedherein. For example, the third entry, or tier, may contain informationidentifying an original mount point for an associated snapshot.

The three tier index may track specific files on a snapshot that are ofinterest. The three tier index describes what is on the disk (or tape),and not just the second tier index description of a file. The third tiermay include an entry including information that identifies where to finddata when needed within the snapshot-based on an indication of whatfiles were on the disk when the snapshot was taken, and where they werelocated.

For example, the index agent 420 creates the index 425 relative to afile system associated with the disk, so as to explain all the files onthat disk and their locations. The index tracks an original mount point,so recovery systems can find network accessible data as and when thedata moves among network resources. For example, an original file named“system.txt” may have an original mount point at“E:/mount/snap1/user1/system.txt,” but the snapshot imaging the file maysubsequently be remounted at a mount point at “F:/user1/system.txt.” Theindex, via the third tier, may track such information, such asinformation associated with movement of the files.

Thus, the file system identifies or presents the files of interest tothe index agent to create the new index. The index maps contextualinformation associated with a snapshot of a volume. The index dataidentifies an application with files of interest. Alternatively oradditionally, the system may employ content indexing functions todiscover content and provide that as a separate content index. Furtherdetails may be found in U.S. patent application Ser. No. 12/058,487,filed on Mar. 28, 2008, entitled METHOD AND SYSTEM FOR OFFLINE INDEXINGOF CONTENT AND CLASSIFYING STORED DATA.

In some examples, the system creates an archive file when creating anarchive copy or other secondary copies of a data set, such as a data setoriginating in a file system. The creation of an archive file enablesthe system, when storing or restoring data, to have both a logical viewand a physical view of stored data. The logical view, represented by thearchive file, enables the system to store data having a format that isneutral (or, independent) with respect to data type. The physical view,represented by an index of locations on stored physical media, enablesthe system to locate the data stored on the physical media as chunks,tape extents, or blocks of the archive file.

The three tier index may include two entries associated with a locationof the file, such as information identifying a snapshot that imaged thefile as well as information identifying a location on secondary storagethat contains the file. An additional entry provides applicationspecific data for the file, such as metadata. Thus, in some cases, thesystem creates a backup copy of a primary volume that includes asnapshot of the primary volume and a three tier index that containsinformation associated with an identification of the file, informationidentifying a location of an archive file associated with the file, andinformation providing application context information about the file(such as an original mount point for the snapshot).

Referring to FIG. 5, a table illustrating a three tier index 500associated with a snapshot is shown. The index 500 includes a fileidentification entry 510 that contains a name of a file, a locationentry 520 that contains location information associated with a primarycopy of the file, a secondary copy of the file, an archive format copyof the file, and so on, and a context or application specific entry 530that provides information about a file system that created the file,such as an original mount point for the snapshot when the file wasimaged by the snapshot. (Of course, the index 500 may include other ordifferent information than what is shown in the Figure). For example,the location entry 520 may identify or provide identificationinformation for the storage media, mount point, tape drive, and so on,associated with creating, updating, and/or storing a copy of the data,such as a secondary copy. In some cases, it may also provide mediaspecific information, such as offsets on a magnetic tape. The locationentry 520 may refer to a storage manager or other data storage resourcewhen identifying a location of a copy, such as a location on a tape.

As one example, the index 500 includes information associated with adata object named “Invention.txt.” This information includes a locationof the archive file for the data object at “archive1” and informationidentifying a mount point for the snapshot that imaged the data object,at “C://snap1/user1.” The index 500 may contain information about somefiles imaged by a snapshot (such as certain files of interest), or maycontain information about all the files imaged by the snapshot. Thesystem may build the index as follows.

Referring to FIG. 6, a flow diagram illustrating a routine 600 forbuilding an index is shown. In step 610, an index agent receives asnapshot of a data set. For example, the snapshot agent within (oroutside of) the media agent 112 creates the snapshot 415 of a primaryvolume of data, and sends the snapshot to the index agent.

In step 620, the index agent 420 receives or obtains context informationassociated with the snapshot. The index agent may query some or all ofthe data storage resources, such as a storage manager or jobs agent, toretrieve data associated with systems and applications that created thesnapshot. For example, the index agent may query the Volume SnapshotService (VSS) provider used to create the snapshot. The index agent mayretrieve information for each of the individual files imaged by thesnapshot, for the entire snapshot, or both. The application contextinformation may include information about resources utilized by thesnapshot agent (such as mount points), information from or about thefile system and/or applications that created the snapshot, and so on.

In addition, the index agent calls the snapshot APIs to identifyinformation associated with the snapshot. Examples of informationreceived from the snapshot APIs include unique snapshot identifiers(which may be received from the snapshot hardware or generated by theindex agent), source host information identifying the computing resourcethat originated the underlying data from which the snapshot was created,volume information, client identifiers, path identifiers, creation time,control host identifiers, source information, server identifiers, jobidentifiers, and so on. For example, the system, via an agent stored ona Microsoft Exchange server, may interact with an external RAID array onthe Exchange server via APIs in order to retrieve information associatedwith snapshots performed on the Exchange server.

In step 630, the media agent stores the snapshot to storage media. Forexample, the media agent 112 transfers the snapshot 415 to storage media430 using one or more of the data paths described with respect toFIG. 1. The media agent may store the snapshot to storage media based ona storage policy, and may select storage media based on the needs of thesystem and on the (future) use of the stored snapshot. For example, thesystem may store the snapshot to magnetic tape for archival purposes.

In step 640, the system stores the received application contextinformation in an index that identifies individual files from the dataset imaged by the snapshot, and in step 650, stores the index to thestorage media. That is, the system builds an index, such as the threetier index described herein, to track information within the snapshotsuch that an original location of the data imaged by the snapshot can bedetermined from the index.

As an example, the system, via an index agent, receives a snapshot takenof a primary volume, such as “snap1.” The system queries a VSS provider,and determines the snapshot occurred at the mount point “D:/users,” andwas performed by a mechanism known to the system as “hardsnapB.” Thesystem then stores the snapshot and the associated information to amagnetic tape, named “tape4,” at location “offset100-230” The systemthen updates an index, such as an index at a media agent that stored thesnapshot, to include information associated the name of the tape withthe name of the snapshot stored on the tape. Thus, an example indexentry may be as follows:

Snap1 D:/users, hardsnapB Tape4, offset100-230

The system may store the entry at the media agent or at other storageresources, such as a global manager. In addition, the system stores theentry along with the snapshot on the tape, to facilitate restoration ofthe data via the snapshot, effectively creating a copy of data (i.e., adata source), using a snapshot of the data.

In addition to creating the index, the system may add data to anexisting archive table file, or other tables, to recognize that aparticular data copy is a snapshot. For example, a flag may be set inthe archive table file to indicate to the system that a copy is asnapshot-based copy. This may facilitate discovery of the copy, forexample.

In some examples, the three-tier or multiple entry index may be storedin different locations across a data storage system. For example,information associated with the location of a snapshot on secondarystorage (such as tape offset information) and the application specificinformation may be stored in a cache of a media agent that transfers thesnapshot to the secondary storage, while the snapshot metadata may bestored by a data management component. Of course, the various indicesmay be stored in other locations in order to meet the needs of thesystem.

Data Recovery Using Snapshot-Based Data Sources

As described herein, the recovery of data, such as individual files, maybe performed by restoring data from snapshot-based secondary copies,such as backup copies. Referring to FIG. 7, a flow diagram illustratinga routine 700 for restoring a data object using a snapshot-basedsecondary copy is shown. In step 710, a data recovery system receives anindication, selection, or request for a data object to be restored. Forexample, the system may present to a user a user interface showing filesavailable for restoration, and receive the request via display elementswithin the user interface. For example, the system may present the filesshown in table 500 of FIG. 5.

In step 720, the system identifies the snapshot that imaged the selectedfile. For example, the system may include a table, map or other datastructure of file names and associated snapshots, and use the map toidentify a snapshot that imaged the file (e.g., table 500 of FIG. 5). Instep 730, the system retrieves or accesses the storage media thatcontains the identified snapshot and an index associated with thesnapshot. For example, if the user wishes to retrieve the file“invention.txt,” the system may retrieve the snapshot that images thefile “invention.txt” in order to identify a location for the file.

In step 740, the system retrieves information from the associated index.For example, the system retrieves the information associated with theselected file, such as information for an archive file associated withthe selected file, information associated with the file system thatcreated the selected file, and so on.

In step 750, the system locates and restores the selected file. Forexample, using the retrieved information from the associated index, thesystem locates the archive file and application specific information forthe selected file, and restores the file.

As an example, a user wishes to restore “email.txt” from a data archive.A data recovery system receives input from the user to restore the file(step 710). The system, via table 500 of FIG. 5, identifies that thesnapshot mechanism snap1 at mount point “D://snap1/user2” performed asnapshot of the file (step 720). The system identifies the location ofthe snapshot on storage media, at “archive 3” (step 730). In thisexample, the information “archive 3” identifies the specific storagemedium as well as the location on the medium. The system then retrievesthe snapshot and uses the retrieved snapshot and known information aboutthe snapshot to locate the file for the user.

Thus, by utilizing a snapshot-based data source as the vehicle for datarecovery, the system is able to take advantage of the speed ofrestoration associated with snapshots with the granularity associatedwith other backup methods, such as restoring individual files. Thedescriptive information in the index enables the system to quickly andefficiently identify the specific location of files imaged by thesnapshot. That is, the combination of an image of a volume of a data(via a snapshot) and knowledge of the mechanisms and resources used tocreate the file system (via an associated index) enables the system torestore data quickly and efficiently.

Seamless Restoration of Data

As described herein, in some cases it may be advantageous to mix or usemultiple, different data storage operations when creating a secondarycopy of a primary volume of data. For example, a data storage systemwill create a full backup of a volume of data at a first point in time,and then incrementally backup the volume in subsequent points in time,only copying changes or modifications made to the volume of data afterthe full backup was created. Often, the full backup is moretime-intensive and system-sensitive than incremental backups, becausemore data is being stored and system resources used during the fullbackup. Thus, a snapshot may be used to create the full backup, andother operations, such as continuous data replication of changes,copy-on-write snapshots, and so on, may be used for the subsequentincremental backups.

Referring to FIG. 8, a flow diagram illustrating a routine 800 forgenerating a secondary copy of a volume of data is shown. In step 810,the system creates a full backup of a primary volume using asnapshot-based copy mechanism. For example, the system performs asnapshot of the primary volume at a first time, stores the snapshot tostorage media, builds an index associated with the snapshot as describedherein, and stores the index to the storage media with the snapshot orotherwise logically links it with that snapshot.

In step 820, the system creates an incremental copy at a second,subsequent time. The system may employ continuous data protection (CDP)or other copy mechanisms, and may transfer data directly to tape orother storage media. CDP is advantageous because it virtually ensures anerror free transfer of data to the tape or to another, often remote,data store. In step 830, the system reviews the volume for any changesto the volume. The system may also review a change journal or othersimilar data structure. When changes are identified, routine 800proceeds back to step 820, and performs an additional backup. Thus, asecondary copy of a volume of data is created and constantly updatedusing backup processes well suited for the various tasks involved.

In order to restore data from such a secondary copy, the system maytreat the different data sources in a similar fashion, thereby providingseamless and efficient data recovery to a user. For example, should theuser wish to restore the entire volume, the system employs the fastsnapshot-based recovery of the original data along with the safe,protected recovery of any subsequent changes to the data set. Inaddition, the system may provide for the restoration of individual filesin a fast and effective manner, because the snapshot-based full backupis able to restore individual files without performing a full restore.Of course, in some cases it may be advantageous to create incrementalcopies as a snapshot-based data source. Additionally, the system maycreate a partial secondary copy as a snapshot-based data source and therest of the secondary copy using other data storage operations.

In some examples, the system restores data from different types ofsecondary copies having different formats, such as snapshots and archivecopies of data. The system may create and leverage an index thatnormalizes, or translates the different data formats during datarecovery. The index may include information that identifies the originallocation of data, information that identifies the current location ofthe data, and/or information that identifies the type of mediacontaining the data. Thus, during a restore process, the system mayreview this index in order to determine a relative path to requesteddata. In some cases, the system may provide a user with some or allversions under management by the system. The system may facilitatesearches across the index, such as those described in U.S. patentapplication Ser. No. 11/931,034, filed on Oct. 31, 2007, entitled METHODAND SYSTEM FOR SEARCHING STORED DATA, which is incorporated by referencein its entirety.

For example, a request for “file1.doc” causes the system to review anindex associating “file1.doc” with an original mount point(D:/snapshot1/) for a snapshot that imaged a volume containing“file1.doc,” and a current location of the snapshot(X:/tape1/snapshot1/file1.doc) now stored in a non-native format. Thesystem can then convert the retrieved copy of the requested file to anative format, identify a path to the original mount point, and providethe requested file.

The system may be employed by current data storage systems that havesnapshot capabilities. For example, the index agent and/or the snapshotagent may be introduced into a data storage system that performssnapshots, but does not utilize them as data sources, enabling the datastorage system to perform the data storage operations described herein.

Additional Functionality

Snapshots of primary data are typically linked to a storage devicestoring the primary data. In some conventional techniques, copying thesnapshot to another storage device may sever links between the copy ofthe snapshot and the primary storage device. As a result, it may bedifficult to recover data from the snapshot copy or analyze the snapshotcopy. However, the techniques described herein provide for copyingsnapshots to a secondary storage device, while maintaining the abilityto recover data from the snapshot copy. Data can be recovered from thesnapshot copy on a full application basis or an individual, granulardata object level (for example, individual files or folders, emailmessages, email folders, database objects, etc.).

The techniques described herein also enable additional uses of snapshotdata. Ancillary applications, such as indexing and search applications,electronic discovery applications, information management applications,tagging applications, as well as other applications, can performfunctions on snapshot data using the same (or at least generallysimilar) techniques used to perform functions on other secondary copiesof data. As previously noted, the techniques described herein mayfacilitate additional uses of snapshot data by, among other things,providing an interface to snapshot data that is the same (or at leastgenerally similar) as an interface used to access secondary copies ofdata created using other techniques, such as backup or copy techniques.

In some examples, this may be done by creating a logical view ofsnapshot data that is identical (or at least generally similar) tological views of other secondary copies of data, such as backup copiesof data. For example, upon creating a snapshot, a record of the snapshotand its metadata may be stored in a data structure that stores recordspertaining to copies of data created by other storage operations, suchas backup or copy operations. In some examples, the snapshot is modeledas if it were another type of secondary copy, such as a backup copy.

FIG. 9 is a block diagram illustrating in more detail certain components900 of the data storage system 150 of FIG. 1. FIG. 9 depicts one of theclients 130, secondary storage computing device 165, secondary storagecomputing device index 161, and storage device 115.

In addition to the data agent 195, the client 130 includes a snapshotcomponent 905, an application 910, and data 915. The application 910 maybe any application executing on the client 130, such as a databaseserver application (for example, Microsoft SQL server, Microsoft ActiveDirectory Server, Oracle, etc.), an email server application (forexample, Microsoft Exchange Server, Apache, etc.), or other types ofservers (for example, application servers such as Microsoft SharePointservers or web servers, virtual machine servers such as MicrosoftVirtual Server, file servers, etc.). The application 910 has associateddata 915, which includes a database 920 and logs 925, shown as logs onethrough n. The application 910 may write data to the database 920 usingtransactional techniques. That is, the application 910 may write changesto the logs 925 before committing the changes to the database 920.

The snapshot component 905 creates snapshots of the data 915 of theclient 130. The snapshot component 905 includes software components andmay also include hardware and/or firmware components. The snapshotcomponent 905 may be provided in its entirety by a single entity (forexample, a single vendor), or the snapshot component 905 may includesub-components that are provided by different entities (such as multiplevendors).

In some examples, the snapshot component includes a Microsoft VolumeShadow Copy Service (VSS) sub-component and a software-based VSSprovider sub-component that is provided by the assignee of the presentapplication, CommVault Systems, Inc. In these examples, the data agent195 interacts with the Microsoft VSS sub-component to create snapshots.The Microsoft VSS sub-component notifies the application 910 to preparethe data 915 for creating a snapshot. The application 910 prepares thedata 915 in an appropriate manner (such as completing open transactions,flushing caches, etc.). The Microsoft VSS sub-component initiates acommit phase and notifies the application 910 that the application 910should be quiesced and to freeze writes to the data 915. The MicrosoftVSS sub-component may also flush a file system buffer and freeze thefile system to ensure that file system metadata is written and that thedata 915 is written in a consistent order. The Microsoft VSSsub-component notifies the VSS provider sub-component to create thesnapshot, and the VSS provider sub-component creates the snapshot. TheMicrosoft VSS sub-component then thaws the file system and notifies theapplication 910 that the application 910 can unquiesce and complete anywrites to the data 915.

In other examples, in addition to or as an alternative to thesoftware-based VSS provider sub-component, the snapshot component 905includes other software-based VSS provider sub-components, such as aMicrosoft system software provider, a Microsoft Data Protection Managerprovider sub-component or a NetApp SnapManager provider sub-component.These other software-based VSS provider sub-components may createsnapshots in manners similar to the manner described in the precedingparagraph, or may use other techniques to create snapshots.

In other examples, in addition to the Microsoft VSS sub-component, thesnapshot component 905 includes one or more hardware-based VSS providersub-components, such as those provided by vendors such asHewlett-Packard, EMC, NetApp, IBM, and other vendors. Thesehardware-based VSS provider sub-components may create snapshots inmanners similar to the manner described in the paragraph above, or mayuse other techniques to create snapshots. Those of skill in the art willunderstand that the snapshot component 905 may include varioussoftware-based and/or hardware-based sub-components and interact withother components in various ways in order to create snapshots of thedata 915.

The snapshot component 905 may create snapshots using varioustechniques, such as copy-on-write, redirect-on-write, split mirror,copy-on-write with background copy, log structure file architecturetechniques, continuous data protection techniques, and/or othertechniques. The snapshot component 905 may store the created snapshotson a particular volume of the client 130.

The secondary storage computing device 165 includes a copy component 940that copies snapshots from the client 130 to another storage device,such as storage device 115. The secondary storage computing device 165also stores certain snapshot information and/or snapshot metadata invarious data structures as described herein. The secondary storagecomputing device 165 may store snapshot information and/or snapshotmetadata in secondary storage computing device index 161.

The secondary storage computing device 165 also includes an interfacecomponent 942. The interface component 942 provides access to the copiedsnapshot data. The interface component 942 can be used to access dataobjects created in other types of secondary copies, such as backupcopies, archive copies, and other types of copies. The interfacecomponent 942 can also be used to display to a user available snapshotsor point in time copies of the data 215 that can be used for recovery orother purposes. The secondary storage computing device 165 also includesa snapshot component 944. The snapshot component 944 may functionsimilarly to the snapshot component 905.

The secondary storage computing device 165 also includes applications945 that perform various functions using copied snapshot data. Theapplications 945 include an indexing component 950, a search component955, an e-discovery component 960, and an information managementcomponent 965. As described in more detail below, the applications 945access copied snapshot data stored on storage device 115 and datastructures stored in secondary storage computing device index 161 inorder to perform various functions.

FIG. 10 is a flow diagram of a process 1000 for analyzing a snapshot.The process 1000 begins at step 1005, where the data agent 195 creates asnapshot of the data 915. At step 1010, the snapshot is copied (forexample, by the secondary storage computing device 165) to storagedevice 115.

As part of copying a snapshot, certain data objects referenced by thesnapshot may also be copied to the storage device 115. For example, thefirst time a snapshot is copied over, all of the data objects (or blocksof data) referenced by the snapshot may also be copied to the storagedevice 115. However, subsequent copying of snapshot may copy over onlydata objects (or blocks of data) that have charged or been modifiedsince the first full copy operation.

At step 1015, the snapshot data is modeled as a copy of the data 915.For example, the secondary storage computing device 165 may storesnapshot information and/or snapshot metadata in secondary storagecomputing device index 161. This information stored in secondary storagecomputing device index 161 may be utilized by the interface component942 to provide the interface to the snapshot data. At step 1020, theapplications 945 access the snapshot data using the interface. At step1025, the applications 945 analyze the snapshot data.

For example, the applications 945 may access the copied snapshot data,extract information (for example, textual information, binary objects,etc.) from the copied snapshot data, and populate one or more indiceswith the extracted information. For example, the applications 945 mayindex content of individual data objects and add information regardingthe content to an index. To do so, the applications 945 may usetechniques such as those described in commonly-assigned U.S. patentapplication Ser. No. 11/694,869 (entitled METHOD AND SYSTEM FOR OFFLINEINDEXING OF CONTENT AND CLASSIFYING STORED DATA), the entirety of whichis incorporated herein.

As another example, the applications 945 may analyze and classify thecopied snapshot data. To do so, the applications 945 may use techniquessuch as those described in commonly assigned U.S. patent applicationSer. No. 11/564,119 (entitled SYSTEMS AND METHODS FOR CLASSIFYING ANDTRANSFERRING INFORMATION IN A STORAGE NETWORK), the entirety of which isincorporated by reference herein. Additionally or alternatively, usersmay provide tags, attributes classifications and/or characterizationsthat are associated with copied snapshot data.

As another example, the applications 945 may single or variable instanceor deduplicate the copied snapshot data. To do so, the applications 945may use techniques described in one or more of previously-referencedU.S. patent application Ser. Nos. 11/269,512, 12/145,347, 12/145,342,11/963,623, 11/950,376, 61/100,686, and 61/164,803.

In some examples, the applications may use techniques described inpreviously-referenced U.S. patent application Ser. No. 12/978,984(entitled “SYSTEMS AND METHODS FOR ANALYZING SNAPSHOTS,”) as part of theprocess of analyzing the copied snapshot data.

At step 1030, the applications 945 store the analysis of the snapshotdata, such as in the secondary storage computing device index 161 and/orin other indices. For example, the indexing component 950 may store theresults of the indexing of the snapshot data in a searchable index sothat the data may be searched by users or other applications usingsearch component 955. As another example, the e-discovery component 960may analyze the snapshot data to identify data that is subject to alegal discovery request or other hold. Once such data is identified, thee-discovery component 960 may copy the data to another location, such asanother storage device 115. As another example, the applications 945 maygenerate a report or display of the analyzed data. After step 1030, theprocess 1000 concludes.

In some examples, the client 130 does not include a data agent 195.Instead, the client 130 includes a software component that createssnapshots. The software component quiesces the application 910, takes afull snapshot of the data 915, monitors changes to the data 915, andcauses changed data to be copied to the storage device 115. The softwarecomponent may then create additional snapshots after the data is copiedto the storage device 115. The software component may use copy-on-writetechniques or other techniques.

Snapshots created by different snapshot providers may have differentformats. Moreover, snapshots created using different techniques may alsodiffer in format. One advantage of the techniques described herein isthat snapshots created by various snapshot providers using varioustechniques can be analyzed by the applications 945. This is due at leastin part to modeling the snapshot data as if it were another type ofsecondary copy and providing a common interface to the snapshot data.This allows the applications 945 to use standard techniques (forexample, standard API functions or other functions) to access thesnapshot data without requiring new or different interfaces to thesnapshot data. Accordingly, the techniques described herein facilitate acommon interface to disparate types of snapshot data.

Another advantage of the techniques described herein is that theyprovide for minimal disruption of production application data. This isdue at least in part to the fact that snapshot creation usually requiresa minimal amount of time to occur, therefore minimizing applicationdowntime. It is also due at least in part to the fact that analysis ofsnapshots typically does not occur on production computing devices,therefore offloading possibly computationally expensive tasks tonon-production computing devices. Another advantage of the techniquesdescribed herein is that they provide the ability to perform value addedoperations on snapshot copies of data even without the originalapplication environment or host being available.

Remote Backup

Remote backup, alternatively referred to as Discrete Data Replication(DDR), enables the maintenance of application and file system data of acomputing device on another storage device. Remote backup synchronizesapplication and file system data of the computing device on the otherstorage device. FIG. 11 is a block diagram of a client 1130 that may beused to perform remote backup according to some examples. The client1130 includes a user mode component 1140 that operates in user mode anda kernel mode file system filter component 1150 and a change journal1155 that operate in kernel mode (the logical distinction between usermode and kernel mode is shown as line 1145).

In some examples, the data 915 of the client 1130 is synchronized usingthe following process. The first time the data 915 is synchronized, theuser-mode component 1140 engages with the application 910 and causes theapplication 910 to be quiesced. The user-mode component 1140 thenperforms or causes to be performed a full copy of the application data915 to a storage device. The user-mode component 1140 may stage the copyin an intermediate location on the computing device before transferringit to the storage device.

After the full copy, the kernel mode file system filter 1150 detectschanges to the application data 915 and records changes in the changejournal 1155. At a scheduled time, the user-mode component 1140 againengages with the application 910 and causes the application 910 to bequiesced. Using the records of changed data recorded in the changejournal 1155, the user-mode component 1140 then copies over data thathas changed since the full copy to the storage device and updates thefull copy. In some examples, each time that an update concludes, theuser-mode component 1140 creates another snapshot of the applicationdata 915. The snapshots could be created by software-based and/orhardware-based components.

Remote backup therefore enables the protection of application data 915in a consistent state and also the restoration of the application data915 to multiple points-in-time. In some examples, application data 915can also be compressed and encrypted during the backup for efficiencyand data security. The integrity of the application data 915 may also beverified during or after the transfer to the storage device.

Creating Snapshots of Virtual Machines

In general, virtualization refers to the simultaneous hosting of one ormore operating systems on a physical computer. Such virtual operatingsystems and their associated virtual resources are called virtualmachines. Virtual machines operate or execute on virtual machine hosts.One example of a virtual machine host is an ESX Server, by VMware, Inc.of Palo Alto, Calif. Other examples include Microsoft Virtual Server andMicrosoft Windows Server Hyper-V, both by Microsoft Corporation ofRedmond, Wash., and Sun xVM by Sun Microsystems Inc. of Santa Clara,Calif. More details as to virtualization may be found in thecommonly-assigned U.S. patent application Ser. No. 12/553,294 (entitledSYSTEMS AND METHODS FOR MANAGEMENT OF VIRTUALIZATION DATA), the entiretyof which is incorporated by reference herein.

Data protection operations such as snapshots can be performed uponvirtual machine data. FIG. 12 is a flow diagram of a process 1200 forcreating snapshots of virtual machines. The process 1200 begins at step1205, where the system discovers one or more virtual machines beinghosted by a primary virtual machine host. At step 1210, the systemcreates snapshots of the virtual machines. The system can employhardware-based snapshot mechanisms and/or software-based snapshotmechanisms to create the snapshots of the virtual machines. For example,the system can utilize a hardware-based snapshot mechanism to create amirrored point-in-time copy of the virtual machines.

In some examples, the system creates the snapshot of the virtualmachines utilizing a virtual machine storage manager. A virtual machinestorage manager is a computing system that does not host virtualmachines but that performs data protection operations on virtual machinedata. In such examples, the virtual machine storage manager contacts theprimary virtual machine host, obtains information about the virtualmachines that the primary virtual machine host is hosting, and utilizessuch information to create the snapshots of the virtual machines.

At step 1215, the system exposes the snapshots to a secondary virtualmachine host that is distinct from the primary virtual machine host. Forexample, the virtual machines may be VMware virtual machines that arehosted by a first ESX Server, and after the system has created thesnapshots, the system exposes the snapshots to a second ESX server thatis distinct from the first ESX server. Exposing the snapshots to thesecondary virtual machine host can include providing read as well aswrite access to the snapshots. At step 1220, the system registers thevirtual machines on the secondary virtual machine host. At step 1225,the system verifies that the snapshots were properly created. The systemcan verify the snapshots by powering on the virtual machines on thesecondary virtual machine host. If the virtual machines are able to bepowered on once registered to the secondary virtual machine host, suchpowering on indicates that the snapshots were properly created. Aftersuch verification, the system can power off the virtual machines on thesecondary virtual machine host. At step 1230 the system analyzes thesnapshots of the virtual machines, as described herein. After step 1230the process 1200 concludes.

One advantage of the process 1200 is that the system can perform it todiscover multiple virtual machines (e.g., tens or even hundreds ofvirtual machines) and create snapshots of the discovered virtualmachines. Such snapshot creation can occur in a short period of time(e.g., on the order of seconds). The system can then verify that thesnapshots were properly created by powering on the virtual machines on asecondary virtual machine host. Such verification can be done with no orreduced impact upon the primary virtual machine host. Another advantageis that the virtual machine data can be analyzed using the snapshots ofthe virtual machines. Other advantages will be apparent to those ofskill in the art.

CONCLUSION

From the foregoing, it will be appreciated that specific examples ofdata storage systems have been described herein for purposes ofillustration, but that various modifications may be made withoutdeviating from the spirit and scope of the system. For example, althoughfiles may have been described herein, other types of content such asuser settings, application data, emails, and other data objects (forexample, blocks of data) can be imaged by snapshots. Accordingly, thesystem is not limited except as by the appended claims.

Terms and phrases used in this document, and variations thereof, unlessotherwise expressly stated, should be construed as open ended as opposedto limiting. As examples of the foregoing: the term “including” shouldbe read as meaning “including, without limitation” or the like; the term“example” is used to provide exemplary instances of the item indiscussion, not an exhaustive or limiting list thereof; the terms “a” or“an” should be read as meaning “at least one,” “one or more” or thelike; and adjectives such as “conventional,” “traditional,” “normal,”“standard,” “known” and terms of similar meaning should not be construedas limiting the item described to a given time period or to an itemavailable as of a given time, but instead should be read to encompassconventional, traditional, normal, or standard technologies that may beavailable or known now or at any time in the future. Likewise, wherethis document refers to technologies that would be apparent or known toone of ordinary skill in the art, such technologies encompass thoseapparent or known to the skilled artisan now or at any time in thefuture.

The presence of broadening words and phrases such as “one or more,” “atleast,” “but not limited to” or other like phrases in some instancesshall not be read to mean that the narrower case is intended or requiredin instances where such broadening phrases may be absent. The use of theterm “module” does not imply that the components or functionalitydescribed or claimed as part of the module are all configured in acommon package. Indeed, any or all of the various components of amodule, whether control logic or other components, can be combined in asingle package or separately maintained and can further be distributedin multiple groupings or packages or across multiple locations.

The description of a synchronization process or synchronizationprocesses is not intended to require that multiple synchronizationsoccur simultaneously or that multiple computing systems beingsynchronized each receive the same data. Although in some examples thedata can be broadcast to all participating computing systemssimultaneously (or close to simultaneously), in other examples the datacan be sent to different computing systems or groups of computingsystems at different times. Likewise, in some examples the same data, orthe same subset of the data can be sent to all computing systems.However, in other examples, subsets of the data can be tailored for agiven computing system or group of computing systems.

Unless the context clearly requires otherwise, throughout thedescription and the claims, the words “comprise,” “comprising,” and thelike are to be construed in an inclusive sense, as opposed to anexclusive or exhaustive sense; that is to say, in the sense of“including, but not limited to.” The word “coupled”, as generally usedherein, refers to two or more elements that may be either directlyconnected, or connected by way of one or more intermediate elements.Additionally, the words “herein,” “above,” “below,” and words of similarimport, when used in this application, shall refer to this applicationas a whole and not to any particular portions of this application. Wherethe context permits, words in the above Detailed Description using thesingular or plural number may also include the plural or singular numberrespectively. The word “or” in reference to a list of two or more items,that word covers all of the following interpretations of the word: anyof the items in the list, all of the items in the list, and anycombination of the items in the list.

The above detailed description of embodiments of the system is notintended to be exhaustive or to limit the system to the precise formdisclosed above. While specific embodiments of, and examples for, thesystem are described above for illustrative purposes, various equivalentmodifications are possible within the scope of the system, as thoseskilled in the relevant art will recognize. For example, while processesor blocks are presented in a given order, alternative embodiments mayperform routines having steps, or employ systems having blocks, in adifferent order, and some processes or blocks may be deleted, moved,added, subdivided, combined, and/or modified. Each of these processes orblocks may be implemented in a variety of different ways. Also, whileprocesses or blocks are at times shown as being performed in series,these processes or blocks may instead be performed in parallel, or maybe performed at different times.

The teachings of the system provided herein can be applied to othersystems, not necessarily the system described above. The elements andacts of the various embodiments described above can be combined toprovide further embodiments.

Any patents and applications and other references noted above, includingany that may be listed in accompanying filing papers, are incorporatedherein by reference. Aspects of the invention can be modified, ifnecessary, to employ the systems, functions, and concepts of the variousreferences described above to provide yet further implementations of theinvention.

These and other changes can be made to the system in light of the aboveDetailed Description. While the above description details certainembodiments of the system and describes the best mode contemplated, nomatter how detailed the above appears in text, the system can bepracticed in many ways. Details of the system may vary considerably inimplementation details, while still being encompassed by the systemdisclosed herein. As noted above, particular terminology used whendescribing certain features or aspects of the system should not be takento imply that the terminology is being redefined herein to be restrictedto any specific characteristics, features, or aspects of the system withwhich that terminology is associated. In general, the terms used in thefollowing claims should not be construed to limit the system to thespecific embodiments disclosed in the specification, unless the aboveDetailed Description section explicitly defines such terms. Accordingly,the actual scope of the system encompasses not only the disclosedembodiments, but also all equivalent ways of practicing or implementingthe system under the claims.

While certain aspects of the invention are presented below in certainclaim forms, the inventors contemplate the various aspects of theinvention in any number of claim forms. For example, while only oneaspect of the invention is recited as embodied in a computer-readablemedium, other aspects may likewise be embodied in a computer-readablemedium. As another example, while only one aspect of the invention isrecited as a means-plus-function claim under 35 U.S.C. §112, sixthparagraph, other aspects may likewise be embodied as ameans-plus-function claim, or in other forms, such as being embodied ina computer-readable medium. (Any claims intended to be treated under 35U.S.C. §112, ¶ 6 will begin with the words “means for.”) Accordingly,the inventors reserve the right to add additional claims after filingthe application to pursue such additional claim forms for other aspectsof the invention.

I/We claim:
 1. A method for creating snapshots of virtual machines,wherein the method is performed by a computing system having a processorand memory, the method comprising: receiving an indication of adiscovery of one or more virtual machines are hosted by a primaryvirtual machine host, creating snapshots of the one or more virtualmachines hosted by the primary virtual machine host, wherein thesnapshots of the one or more virtual machines reference multiple dataobjects; creating at least one index associated with the snapshots,wherein the index includes context information related to logicallocations of copies of the multiple data objects referenced by each ofthe snapshots; exposing the snapshots of the one or more virtualmachines to at least one second virtual machine host; registering theone or more virtual machines on the at least one second virtual machinehost via the exposed snapshots; powering on the one or more virtualmachines on the at least one second virtual machine host; verifying thatthe snapshots of the one or more virtual machines were properly createdbased on the powering on of the one or more virtual machines on the atleast one second virtual machine host; and in response to verifying thatthe snapshots were properly created, powering off the one or morevirtual machines on the at least one secondary virtual machine host. 2.The method of claim 1 wherein the method further comprises accessing oneor more of the multiple individual data objects.
 3. The method of claim1 wherein the snapshots references at least one set of data associatedwith an application, and wherein the application includes an emailserver, a Structured Query Language (SQL) server, a file server, or anapplication server.
 4. The method of claim 1 wherein creating snapshotsincludes creating the snapshots at least partly with a hardware-basedsnapshot provider.
 5. A non-transitory computer-readable storage mediumwhose contents cause a computing system to create snapshots of virtualmachines, wherein the computing system has a processor and memory,comprising: receiving an indication of a discovery of one or morevirtual machines are hosted by a primary virtual machine host, creatingsnapshots of the one or more virtual machines hosted by the primaryvirtual machine host, wherein the snapshots of the one or more virtualmachines reference multiple data objects; creating at least one indexassociated with the snapshots, wherein the index includes contextinformation related to logical locations of copies of the multiple dataobjects referenced by each of the snapshots; exposing the snapshots ofthe one or more virtual machines to at least one second virtual machinehost; registering the one or more virtual machines on the at least onesecond virtual machine host via the exposed snapshots; powering on theone or more virtual machines on the at least one second virtual machinehost; verifying that the snapshots of the one or more virtual machineswere properly created based on the powering on of the one or morevirtual machines on the at least one second virtual machine host; and inresponse to verifying that the snapshots were properly created, poweringoff the one or more virtual machines on the at least one secondaryvirtual machine host.
 6. The non-transitory computer-readable storagemedium of claim 5, further comprising accessing one or more of themultiple individual data objects.
 7. The non-transitorycomputer-readable storage medium of claim 5 wherein the snapshotsreferences at least one set of data associated with an application, andwherein the application includes an email server, a Structured QueryLanguage (SQL) server, a file server, or an application server.
 8. Thenon-transitory computer-readable storage medium of claim 5 whereincreating snapshots includes creating the snapshots at least partly witha hardware-based snapshot provider.
 9. A system to create snapshots ofvirtual machines, comprising: at least one processor; at least onememory; a receiving component configured to receive an indication of oneor more virtual machines, a creating component configured to createsnapshots of the one or more virtual machines hosted by a primaryvirtual machine host, wherein the snapshots reference multiple dataobjects, and configured to create at least one index associated with thesnapshots, wherein the index includes context information related tological locations of copies of the multiple data objects referenced byeach of the snapshots; an exposing component configured to expose thesnapshots of the one or more virtual machines to the at least one secondvirtual machine host; a registering component configured to register theone or more virtual machines on the at least one second virtual machinehost; and a powering component configured to power on the or morevirtual machines on the at least one second virtual machine host,wherein powering on of the one or more virtual machines on the at leastone second virtual machine host verifies that the snapshots of the oneor more virtual machines were properly created, and configured to poweroff the one or more virtual machines on the at least one secondaryvirtual machine host after the verification that the snapshots wereproperly created.
 10. The system of claim 9, further comprising anaccessing component configured to access one or more of the multipleindividual data objects.
 11. The system of claim 9 wherein the snapshotsreference at least one set of data associated with an application, andwherein the application includes an email server, a Structured QueryLanguage (SQL) server, a file server, or an application server.
 12. Thesystem of claim 9 wherein the creating component is associated with ahardware-based snapshot provider.